Field of the Invention
The present invention relates to a device for supplying fuel to an engine, the fuel supply device being provided with a fuel supply route for supplying an engine with fuel collected in a fuel tank, and a filter and a first fuel pump being provided to the fuel supply route in the stated order from the upstream side of a fuel supply direction.
Description of Related Art
In a fuel supply device of such description, impurities included in the fuel are removed by the filter provided to the fuel supply route, and the fuel from which the impurities have been removed is supplied to the engine. Also, a fuel return route for returning fuel coming from the engine to the fuel tank is provided, so that surplus fuel in the engine is returned to the fuel tank by the fuel return route.
In the fuel supply device of such description, although the impurities are removed by the filter, in a case where low-temperature fuel is being supplied to the filter, such as initial start-up of the engine when in a cold climate, a problem emerges in that deposited matter or the like is created from the fuel and the filter is clogged by the deposited matter.
In view whereof, in a conventional fuel supply device, an interconnecting flow path that creates communication between a midway site of the fuel supply route and a midway site of the fuel return route is provided, and a circulation valve of a temperature-sensitive displacement type is provided to the interconnecting flow path (see, for example, Japanese Laid-open Patent Application 2007-16658).
In the apparatus described in Japanese Laid-open Patent Application 2007-16658, the circulation valve opens the interconnecting flow path in a case where the fuel temperature is less than a predetermined temperature, whereby the comparatively higher-temperature fuel returning from the engine to the fuel tank is admixed into the fuel coming from the fuel tank and is supplied to the filter. The temperature of the fuel being supplied to the filter is thereby elevated, thus preventing clogging of the filter. Also, the circulation valve closes off the interconnecting flow path in a case where the fuel temperature is the predetermined value or greater, whereby the full amount of surplus fuel coming from the engine is returned to the fuel tank.